Blast-relatedtraumaticbraininjury(TBI)isassociatedwithavarietyofmentalhealthdisordersinveterans includingpost-traumaticstressdisorder(PTSD)anddepression.Theseconditionshavebeenparticularly commoninveteransreturningfromtherecentconflictsinIraqandAfghanistan.Treatmentsforthechronic symptomsthatfollowblast-relatedTBIarecurrentlylimitedtolargelysupportivecare.Wehaveexploredthe effectsof74.5-kPablastexposuresthatmimicmildTBI(mTBI)inaratmodel.Blast-exposedratsexhibiteda varietyofPTSD-relatedbehavioraltraits,includingincreasedanxiety,enhancedacousticstartle,altered responsestoapredatorscent,andalteredcuedfearresponsesthatarechronicandpersistent.Thecerebral vasculatureisespeciallysensitivetoblastinjurywithbothacuteandchronicvascularpathologybeingpresent afterblast-exposure.Theoverallgoaloftheproposedresearchistotestwhetherphotobiomodulationtherapy usingtranscraniallasertherapy(TLT)canimprovethechronicanxietyandPTSD-relatedbehavioraltraits observedinblast-exposedratswhileamelioratingtheunderlyingvascularpathology.BeneficialeffectsofTLT havebeenshowninbothhumansandanimalmodelsforarangeofneurologicalandpsychologicaldisorders includingTBI.WeproposetoadministerTLTtoblast-exposedratsatsixmonthsafterblastexposure,atime whenthePTSD-relatedbehavioralphenotypeiswellestablished.WewilldeterminewhetherTLTcanreverse thebehavioraleffectsofblastinjuryusingatestingstrategythatwillfocusonthosetestspreviouslyfoundmost informative.Wewilldetermineusingmicro-CTscanning,quantitativehistopathologyandbiochemistrywhether blastassociatedvascularpathologycanbereversedbyTLT.Collectively,thesestudieswillexplorethe potentialtherapeuticbenefitsoftranscranialphotobiomodulationforthetreatmentofblast-relatedbehavioral effects.Thesestudiesmayuncovernewtherapeuticoptionsforthetreatmentofveteransaffectedbythe chroniceffectsofblast-relatedinjury.